© Strojni{ki vestnik 48(2002)9,491-500                 © Journal of Mechanical Engineering 48(2002)9,491-500
ISSN 0039-2480                                                                                                                        ISSN 0039-2480
UDK 621.311.21:621.224.1                                                                     UDC 621.311.21:621.224.1
Strokovni ~lanek (1.04)                                                                                                          Speciality paper (1.04)
Nekateri  vidiki  terenskih  preskusov peltonovih turbin v HE “Peru}ica”
Some Aspects of the Research Carried out on the Power Generation Units at the Peru}ica Hydroelectric Power Plant
Milo Mrki} - Zoran Culafi}
V delu so predstavljeni osnovni delovni parametri HE “Peručica”, prikazana je analiza delovnega procesa v Peltonovi turbini in eksperimentalno-analitična metoda za določitev pretočne karakteristike sob vgrajenih v HE “Peručica” pri obratovalnih pogojih. © 2002 Strojniški vestnik. Vse pravice pridržane. (Ključne besede: turbine Peltonove, parametri energetski, karakteristike procesov, metode eksperimentalne)
This paper describes the basic power parameters of the “Peručica” HEPP Also included is an analysis of the work process in the Pelton turbine and an experimental-analytical method for determining the nozzle-flow characteristics under real working conditions. © 2002 Journal of Mechanical Engineering. All rights reserved. (Keywords: Pelton turbines, power parameters, process characteristics, experimental methods)
0 UVOD
Hidroelektrarna “Peručica” ima moč 307 MW. Zgrajena je bila v treh fazah, prva faza se je začela leta 1960. Hidroelektrarna je derivacijskega tipa in ima skupaj sedem agregatov vodoravne izvedbe s Peltonovimi turbinami.
Prvi avtor prispevka je delo začel kot hidroinženir v tej elektrarni leta 1964, zaposlen z reševanjem obratovalnih problemov. V dolgem času delovanja elektrarne so bila opravljena raziskovanja mnogih pojavov v dejanskih razmerah, da bi zagotovili pogonske stabilnosti. Pri neposrednem učenju pogonskega osebja so bila v raziskovanja vključene domače strokovne institucije. Avtor je pri vseh raziskovanjih sodeloval neposredno ali kot svetovalec.
Glede na bogato znanje in izkušnje, pridobljene v času delovanja hidroelektrarne, je avtor v svojem delu podal vidike, pridobljene pri eksperimentalnih raziskovanjih v dejanskih razmerah in iz tega izhajajoče metode analitičnega določanja pretočnih karakteristik Peltonovih turbin, vgrajenih v obravnavani hidroelektrarni.
0 INTRODUCTION
The Peručica hydroelectric power plant (HEPP) has an installation power of 307 MW. It was built in three phases, and the first phase began operating in 1960. It was built as a derivative type, and it has seven power-generation units of the horizontal type with Pelton turbines.
One of the authors of this paper started work as a hydro engineer at this HEPP in 1964, when he was working on some problems concerning exploitation. During the long exploitation period of this HEPP a lot of research was conducted on many occurrences in stationary and non-stationary regimes under real conditions. In order to acquire operational staff, other qualified domestic and scientific institutions were engaged. In all this research the author participated directly or as a consultant.
Having gained much experience during the exploitation period of this HEPP, from the very beginning to the present day, the author presents some aspects of the completed experimental research under real conditions, and the method of analytically determining the flowing exploitation characteristic of the Pelton turbines mounted in this HEPP.
gfin^OtJJIMISCSD
02-9
stran 491          |^BSSITIMIGC
Mrki} M. - Culafi} Z.: Nekateri vidiki terenskih preskusov - Some Aspects of Research
1 OSNOVNI ENERGETSKI PARAMETRI TURBIN V PRIMERU HE PERUČICA
Za vsak hidroenergetski sistem so karakteristični osnovni delovni parametri bruto in čisti padec ter instalirani pretok. V že zgrajenih hidroelektrarnah obratujejo turbine pod določenimi energetskimi parametri, od katerih so nekateri lahko stalni, večina pa se jih spreminja glede na funkcijo delovnega režima. Med osnovne parametre vodnih turbin spadajo: moč (P), pretok (Q), specifična energija (Y), izkoristek (h) in število vrtljajev turbine (n).
Specifični energiji vodnega toka (Y, Y) na gladini vode zgornje akumulacije V GNV (indeks g) in na gladini vode spodnje akumulacije VDNV (indeks d) sta za splošni primer hidroenergetskega sistema izraženi z enačbama:
1 BASIC POWER PARAMETERS OF THE PELTON TURBINES ON THE PERUČICA HEPP
The basic characteristic working parameters of any hydroelectric power plant are the gross and the net fall and the installed flow On the hydroelectric power plants that are already built the turbines operate with certain power parameters, some of which can be permanent, whereas most of them change depending on the function of the working mode. The basic parameters of water turbines include the following: power (P), flow (Q), specific energy (Y), degree of efficiency (h) and the number of revolutions (n).
The specific energies of the water flow (Yg, Yd) on the surface of the upstream reservoir V GNV (index g) and on the surface of the downstream reservoir V DNV (index d) on the Peručica hydroelectric power plant with Pelton turbine are:
p                   c
g     r    g    g     2
2
r
(1), (2).
Razlika energij Y in Yd pomeni bruto specifično energijo hidroelektrarne (Ybr).
The difference between the specific energies Yg and Yd represents the gross specific fall in the flow of the electrical power plant (Ybr).
Sl. 1. Razporeditev hidroagregata s Peltonovo turbino, vgrajenega v HE “Peručica” Fig. 1. General arrangement of power generation unit with Pelton turbine in the Peručica HEPP
VH^tTPsDDIK
stran 492
Mrki} M. - Culafi} Z.: Nekateri vidiki terenskih preskusov - Some Aspects of Research
V (1) in (2) so: pg in pd tlaka na nivojih (g - g) in (d - d), c in cd srednji hitrosti v prerezih, z in zd koti zgornjega in spodnjega nivoja vode hidroelektrarne, g je zemeljski pospešek.
Za Peltonove (akcijske) turbine z eno šobo (agregati I do V v HE “Peručica”) je razpoložljiva specifična energija:
The designations in (1) and (2) are as follows: pg and pd - absolute pressure at levels (g- g) and (d -d), cg and cd - mean velocities in the cross-sections, zg and zd - elevations of upstream and downstream water surface, g - acceleration due to gravity.
For the Pelton (action) turbines with one nozzle (power generation units I–V) the available specific energy:
pm       c1
Y = g.H = r + 2 + g-(z1 + a-z2)
(3),
kjer so: z1 - kota vstopnega prereza turbine, a -oddaljenost kote težišča vstopnega prereza do kote vgradnje manometra, z2 - kota točke, kjer os šobe tangira osnovni krog turbinskega kolesa, p -manometrični tlak, H - neto padec.
Hitrost c2 na izstopnem prerezu turbine (izhodni rob Peltonove turbine) je zanemarljiva (c << c1).
V primeru, ko ima turbina dve šobi z enakim pretokom (agregati VI in VII v HE “Peručica”), se kota z2 določa kot srednja vrednost kot točk A in B (sl. 1). Vse hitrosti, podane v prejšnjih enačbah, so srednje hitrosti, ki se določajo s pretokom Q in pretočnim prerezom A, tj. po enačbi C= Q /Ai. i      i Moč vodnega toka se določa z enačbo:
where: z1 - the elevation of the turbine inlet cross section, a - the distance between the elevation of the centre of gravity of the inlet cross section and the elevation of the installation of the pressure gauge, z2 - the elevation of the point where the nozzle axis touches the basic circle of the turbine wheel, pm - the overpressure indicated by the pressure gauge, H - the net turbine fall.
The velocity c2 at the turbine outlet cross section (outlet edge of the Pelton turbine) is low (c2 <<c1).
In the event that the turbine has two nozzles with the same flow rate (units VI–VII) the elevation z2 mean is determined as the mean value of the elevation of points A and B (Figure 1.). All velocities given in the preceding equation are the mean velocities determined by means of the flow (Q) and the flow cross section A, i.e. according to the equation ci = Qi /Ai.
The power of the water flow is determined with the following equation :
na gredi turbine pa z enačbo:
pri čemer je r gostota vode
Ps=r-g-Q-H
and the mechanical power of the turbine:
Ps=r-
¦Q-H-h
where r is water density.
(4),
(4'),
2 KARAKTERISTIKE DELOVNEGA POSTOPKA V PELTONOVI TURBINI
Slika 2 prikazuje karakteristike moči in izkoristka dvojne Peltonove turbine 2 • P • 2,1 / 255 (pri čemer so: 2 - število delovnih koles hidroagregata; P - Peltonova turbina z dvema delovnima kolesoma; 2,1 - premer delovnega kolesa v m; 255 - premer vstopa v mm),
Karakteristike so dobljene pri preskusu garantiranih parametrov III faze HE “Peručica” pri padcu H = 526 m in pretoku Q = 12,75 m3/s.
Gonilnik Peltonove turbine izkorišča samo kinetično energijo vodnega toka. Zaradi tega mora spremeniti pretočni aparat turbine (šob) ustrezno rezervo energije vodnega toka v kinetično energijo.
Razpoložljivi padec (višina) na izstopu izšobe je:
c2 2-g
2 CHARACTERISTICS OF THE WORK PROCESS IN A PELTON TURBINE
Figure 2 shows the characteristics of the power and the degree of efficiency of the double Pelton turbine 2 ¦ P ¦ 2.1 / 255 (where: 2 is the number of working wheels of the power generation unit, P is the Pelton turbine with two nozzles, 2.1 is the diameter of working wheel [m], and 255 is the nozzle diameter [mm]).
The characteristics are obtained experimentally when testing the guaranteed parameters of the stage III of the Peručica HEPP at the fall H = 526 m and the flow Q = 12.75 m3/s.
The runner of the Pelton turbine only uses the kinetic energy of the water flow. Therefore, the flow device of the turbine (nozzle) must convert the relevant reserve of the water flow energy into kinetic energy.
The kinetic energy at the nozzle outlet is:
H-hm
(5),
Mrki} M. - Culafi} Z.: Nekateri vidiki terenskih preskusov - Some Aspects of Research
				h			59695
					P		52199
							44742
							37285
							29828
							22371
							14914
							
91
88
87

85
35       7
Q (m3 /s)

Sl. 2 Diagram izkoristka in moči Peltonove turbine 2 . P . 2,1/255 (padec H=526 m , pretok Q=12,75 m3/s) Fig. 2 Diagram of degree of efficiency and power of the Pelton turbine 2 . P  . 2.1/255 in case of fall H =
526 m and Q = 12.75 m3/s
pri čemer so: H - razpoložljiva višina pred šobo; c -pretočna hitrost; hm - izkoristek šobe.
Torricellijeva enačba za hitrost iztekanja tekočine skozi odprtino pri nespremenljivi višini je:
where: H - the available height at the nozzle, c - the flow velocity, hm - the degree of efficiency of the nozzle.
The well-known Torricellian formula for the velocity of a liquid flow from an opening at constant water level is:
2g-H-hm =jyj2g-H
pri čemer je: j =   hm - koeficient hitrosti iztekanja. Šoba Peltonove turbine ima krožno izhodno odprtino in osnosimetrični natok, kar zagotavlja
(6),
where: j =  hm - the coefficient of the discharge velocity.
The nozzle of the Pelton turbine has a circular
outlet opening and axially symmetrical in flow
Sl. 3. Lega delovnega kolesa in šobe Peltonove turbine Fig. 3 Position of mounting of the runner and nozzle of the Pelton turbine
grin^sfcflMISDSD
^BSfiTTMlliC |        stran 494
90
89
86
84
9
11
13
Mrki} M. - Culafi} Z.: Nekateri vidiki terenskih preskusov - Some Aspects of Research
stabilne, praktično valjne tokove na izhodu (slika 3).
Specifičnost delovnega postopka v Peltonovi turbini je v tem, da sprememba hitrosti vrtljajev gonilnika ne vpliva na pretočno moč turbine, tj. med momentom na osi turbine in parametri vodnega toka ni povratnega vpliva. Pretočna karakteristika šobe ni odvisna od obratovalnega režima, profila in izmer gonilnika. Odprtja šobe so v karakterističnem diagramu Q - n11 (Q11 je enotski pretok, n je enotska vrtilna frekvenca) predstavljena s premicami, ki so vzporedne z absciso (n11). Zaradi tega pri Peltonovih turbinah odprtino pretočnega aparata, gib igle šobe (s) ne definiramo glede na premer delovnega kolesa. Relativni gib igle s’ se izraža glede na premer izhodne odprtine šobe d po enačbi (sl. 3):
ensuring stable, practically cylindrical flow at the outlet (Figure 3).
It is a specific feature of the working process in the Pelton turbine that the change of rotating speed of the runner does not affect the flow rate of the turbine, i.e. there is no return influence between the turbine shaft torque and the water flow parameters. The flow characteristic of the nozzle does not depend on the mode of working, the runner contours and the dimensions. The nozzle openings in the characteristic diagram Q11 – n11 (Q11 is the unit pressure, n11 is the unit rotating speed) are given with straight lines parallel to the abscissa (n11). Therefore, for these turbines it is not rational to express the flow device opening, nozzle needle motion (s), with regard to the working wheel diameter. The relative needle motion (s’) is expressed with regard to the diameter of the nozzle outlet opening (dm) (Figure 3), i.e.:
= sdm
(7).
Pri Peltonovih turbinah izrazimo karakteristično površino Am in pretok šobe Qm z enačbami (cx= ^2-g-H ):
It is appropriate in the case of the Pelton turbine to express the characteristic surface and nozzle flow (Ax ; Q ) by means of equations (c =2^H):
A   =d2-J4    in / and   Q
xm            ml                                             x
(8),
pri čemer indeks “x” označuje poljuben delovni režim, D - osnovni premer gonilnika.
Z uporabo karakterističnih veličin (8) definiramo brezdimenzijski pretočni koeficient šobe Peltonove turbine k:
 Qm               4Qm
where the index “x” designates the characteristic mode of working, D1 is the basic diameter of the working wheel. By means of these characteristic values (8) the unit flow of the nozzle of the Pelton turbine (kg) is defined :
Qx
takole:
•2ndm2^gH Glede na enačbo (6) lahko pretok šobe izrazimo
0,901
Qm
d2mJgH
(9).
On the basis of equation (6) it is possible to express the nozzle flow as follows:
Qm      4  js2gH
(10),
pri čemer je d0 premer vodnega curka, d pa premer šobe (sl. 3).
Nadalje lahko enotni pretok šobe izrazimo tudi z enačbo:
where do is the diameter of the water jet, dm is the diameter of the nozzle (Figure 3.).
Further, the unit nozzle flow can be expressed by the equation:
j{dodm
(11).
3 GEOMETRIJSKI PARAMETRI ŠOB, VGRAJENIH V HE “PERUČICA”
V HE “Peručica” je vgrajenih 7 agregatov z dvojno Peltonovo turbino vodoravne izvedbe. Na
kolesa z dvema šobama tipa 2 . P . 2,1 / 255 ga
Na sliki 4 je prikazan profil izstopnega dela šobe na agregatih HE “Peručica”. Osnovni geometrijski parametri šobe so: d - premer izhodne odprtine (d = 300 mm), A = d m p / 4 - površina
3 GEOMETRIC PARAMETERS OF NOZZLES INSTALLED ON THE PERUČICA HEPP
On the Perucica HEPP seven power-generation units with double Pelton turbines in the horizontal position are
are equipped with two nozzles of type 2 . P 2 2.1 / 255.
Figure 4 shows the contour of the outlet part of the nozzle on the Peručica HEPP The basic geometrical parameters of the nozzle are: d is the diameter of outlet opening (dm = 300 mm), Am = d m . p / 4 is the surface of
| IgfinHŽslbJlIMlIgiCšD I stran 495
glTMDDC
Mrki} M. - Culafi} Z.: Nekateri vidiki terenskih preskusov - Some Aspects of Research
Sl. 4 Profil izstopnega dela sobe, vgrajene v HE “Perucica” v poljubni legi “i-i” Fig.4. Contour of outlet part of the nozzle installed on the Perucica HEPP in arbitrary position “i-i”
izhodnega pretočnega prereza (A = 70650 mm2), s -gib igle šobe, smaks - največji gib šobe (smaks = 195 mm), a - kot igle šobe (a =57,2o), h - višina odprtine šobe, him - največja višina odprtine šobe, (him = 90 mm), Di - premer okrova na “i - i”, d - premer ile v prerezu (i - i), g - izstopni kot šobe. i
4 DOLOČITEV PRETOČNE KARAKTERISTIKE ŠOBE NA IZVEDBI
Pretok šobe se lahko glede na enačbi (10) in (11) izrazi kot:
the outlet flow cross section (Am = 70650 mm2), s is the nozzle needle motion, smax is the maximum nozzle motion (smax=195 mm), a is the nozzle needle angle (a =57,2o), h is the height of nozzle opening, himax is the maximum height of the nozzle opening (h max= 90 mm), Di is the diameter of housing “i-i”, di is the diameter of the needle in cross section (i-i), g is the outlet angle of the nozzle.
4 DETERMINATION OF NOZZLE FLOW CHARACTERISTICS UNDER REAL CONDITIONS
With respect to equations (10) and (11) the nozzle flow can be expressed as:
Qm=kgAmj2gH
(12).
Razpoložljiva višina šobe (H) je definirana z enačbo:
The available height of the nozzle (Hm) is defined by the equation:
H = Hb -DH1 -DH2
(13),
pri čemer sta: H - bruto višina HE “Perucica” (H = 550 m), AH1 - hidravlične izgube v dovodnem sistemu od vtočne zgradbe do izhoda iz razvejanja (sl. 1).
Izgube v dovodnem sistemu HE “Perucica” (AH1) so izmerjene po delih na vstopni rešetki, v predoru, na razvejanju v izravnalniku in v dovodnih cevovodih (slika 5).
Rezultati meritev izgub po posameznih cevovodih (leta 1998) so:
-    cevovod 1 (agregati 1, 2; dolžina L = 1851 m; premer D = 2,2 m - 1,8 m): ÄHc1-0,0563-Q2 1,
-    cevovod 2 (agregati 3, 4, 5; dolžina L = 1883 m; premer D = 2,2 m - 2,1 m): AH 2=0,0407 •Q2c2,
-    cevovod 3 (agregati 6, 7; dolžina L = 1931 m; premer D = 2,5 m - 2,2 m):   Hc3=0,02297-Q2c3.
where: H is the gross water level of the Perucica HEPP (H = 550 m), AH1 is the hydraulic loss in the supplying system from the intake structure to the bifurcation outlet (Figure 1).
The losses in the supply system of the Perucica HEPP (AH1) are measured according to the sections in entering the trash rack, in the tunnel, in the surge tank and in the supply pipelines. (Figure 5).
The measured results of the losses according to the branches of the pipeline (in 1998) are:
-    pipeline 1 (units 1, 2; length L = 1851 m; diameter D = 2.2 m - 1.8 m):AHc -0.0563-Q21,
-    pipeline 2 (units 3, 4, 5;Clength L = 1883 m; diameter D = 2.2 m - 2.1 m):AHc2 = 0.0407-Q22,
-    pipeline 3 (units 6, 7; length L = 1931 m; diameter D = 2.5 m - 2.2 m):AHc3=.0.02297-Q2c3.
VH^tTPsDDIK
stran 496
Mrki} M. - Culafi} Z.: Nekateri vidiki terenskih preskusov - Some Aspects of Research
konec predora end of tunnel
Tt~          konec cevovoda
¦^   end of pipeline
Sl. 5 Pretočni sistem HE “Peručica” Fig. 5 Flow system of Peručica HEPP
Srednja vrednost koeficienta izgub je:
a)   rešetka:      kr = 0,749.103
b)   predor:        kt = 1,261.10-3
c)   izravnalnik: k1 6,50.103
k2 = 4,66.10-3 k3 = 5,31.103 Pretok šobe oziroma koeficient pretoka sta odvisna od giba igle šobe s:
The average value of the loss coefficient is :
a)   in trashrack:    kr = 0.749.10-3
b)   in tunnel:        kt = 1.261.10-3
c)   in surge tank: k1 = 6.50.10-3
k2 = 4.66.10-3 k3 = 5.31.10-3 The nozzle flow and/or the flow coefficient depend on the nozzle needle motion (s), therefore:
k   , =------Q
gW    Am2g-H
(14).
V primeru hidroelektrarne “Peručica” lahko predpostavimo nespremenljivo vrednost višine H pri vseh delovnih režimih elektrarne (glede na veliko bruto višino (Hb * 550 m) in s tem tudi relativno zanemarljiv vpliv izgub višine v dovodnem sistemu pri spremembah pretokov v delovnem področju turbine).
Z merjenjem pretoka Q (s) za znane vrednosti A in H lahko s preskusi določimo odvisnost koeficienta pretoka k (s) od relativnega giba igle šobe s’ (enačba 7).
V   obsegu raziskav nestalnih režimov obratovanja v sistemu HE “Peručica”, je bila določena karakteristika šobe k = f(s/d) agregatov I-V. Karakteristika je grafično prikazana na sliki 6. Delovno področje agregatov VI - VII je:
In the case of the Peručica HEPP the constant value of height H for all working modes of the power plant (with respect to the great gross water level (Hb * 550 m) and, consequently, a relatively unimportant influence of height losses in the adduction system in the case of changes to the flow in the turbine working area is assumed.
Thus, by measuring the flow Q (s) for the known values Am and Hm the dependence of the flow coefficient k (s) on the flow Q(s) and/or on the relative nozzle needle motion (equation 7) is experimentally determined.
Within the scope of research on the unstable working modes of the Peručica HEPP the nozzle characteristic k = f(s/d) of units I-V graphically shown in Figure 6 was determined. The working range for the Peručica III power generation units is :
Hmax = 526 m; Hmin = 520 m; n = 428,5 min-1;
Q11 = 63,0 l/s; n11 = 39,2 min-1; P = 59 MW;
(D1 = 2100 mm, d0 = 225 mm, j = 0,614)
Parametri agregatov I - V so:
The parameters of the units I–V are :
n = 375 min-1, P = 39 MW, Q = 8,5 m3/s, D1 = 2400 mm, d0=300 mm
Ker se pretok Q na izhodu iz šobe s spremembo giba igle s spreminja zaradi spremembe površine dejanskega pretočnega prereza, skozi katerega prehaja voda in spremembe polja hitrosti vode v šobi, lahko enačbo za pretok napišemo v obliki:
As the flow Qm at the nozzle outlet changes with the needle motions due to the change of surface of the effective flow cross section through which the water passes and the change of the water speed in the nozzle, the equation for the flow can be written in the following form:
Q(s/dm) = c(s/dm)A(s/dm)
(15).
| IgfinHŽslbJIMlIgiCšD I stran 497
glTMDDC
Mrki} M. - Culafi} Z.: Nekateri vidiki terenskih preskusov - Some Aspects of Research
Glede na (12) velja:
s/iW-]
Sl. 6. Karakteristika sobe kQ = f (s/dm) agregatov I-IV Fig. 6. Nozzle characteristic kQ = f (s/dm) of units I-IV
Taking into account (12), the following applies:
k Q A m   2g~H=cA(s/d m )                                                            (16)
5 SKLEP
Prvo vprašanje, na katerega mora odgovoriti projektant Peltonove turbine, je izbira njenih osnovnih parametrov; konstrukcijske skice same turbine, hitrosti vrtenja, število šob, premer delovnega kolesa, premer šobe itn. Pri tem se razume, da so meje sprememb vodnega padca in mejna moč po navadi podane s projektno nalogo.
Rešitev te naloge ni enolična. Praktično je treba analizirati več možnih variant. Za končno rešitev se odločimo po vsestranski tehnično-gospodarni analizi.
Svetovne izkušnje potrjujejo, da so v 60. letih v gradili Peltonove turbine z vodoravno gredjo z eno ali največ dvema šobama na en gonilnik. Po tem obdobju pa so prišli iz vodoravne v navpično izvedbo. Namen projektantov je bil, da se poveča število šob na gonilnik. Tako so sodobne velike Peltonove turbine najpogosteje izvedene z navpično gredjo in šestimi šobami na en gonilnik.
Peltonove turbine v HE “Peručica” imajo vodoravno gred z dvema gonilnikoma na enoto (I do V) oziroma dvema šobama na enoto (VI in VII) za en gonilnik.
Rezultat raziskav nestalnih režimov obratovanja je pretočna karakteristika šobe 2 . P . 2.4 / 300 Peltonove turbine 2 . P1 . 2.4 / 300 (enote I do V) (slika 6).
5 CONCLUSION
The first question that should be answered by the design engineer of the Pelton turbine is the selection of its basic parameters: the design sketch of the turbine alone, the number of revolutions, the nozzle number, the diameter of the runner, the diameter of the nozzle, etc. It goes without saying that the limits of the changing fall and the limited power are usually set in the design assignment.
The solution of this assignment is not uniform. It is necessary to analyze practically several possible variants. The final solution to the problem is adopted after the comprehensive tech-eco analysis.
General practice around the world showed that in the 1960s Pelton horizontally mounted turbines with one or a maximum of two nozzles for one runner were built. After that period they moved from horizontal to vertical mounting. That is, in the first place, the result of the designer’s desire to increase the nozzle number for the runner. The modern Pelton turbines are usually built with a vertical shaft and with six nozzles in one working circle.
Pelton turbines’ HEPPs have a horizontal shaft with two runners and with one (I–V) or two nozzles for one runner (VI and VII).
A result of the research into unstable operat-ing modes is the nozzle flow characteristic kg =f(s/
.. dm) of the Pelton turbine 2  P1 2.4 / 300 (units I–V)
(Fig. 6) .
VH^tTPsDDIK
stran 498
Mrki} M. - Culafi} Z.: Nekateri vidiki terenskih preskusov - Some Aspects of Research
6 OZNAKE 6 SYMBOLS
oddaljenost kote težišča vstopnega prereza do kote vgradnje manometra
površina izhodnega pretočnega prereza
pretočna hitrost
srednja hitrost v prerezu (g - g)
srednja hitrost v prerezu (d - d)
osnovni premer gonilnika
premer okrova na “i - i”
premer igle v prerezu (i - i)
premer vodnega curka
premer izhodne odprtine šobe
čisti padec
bruto padec hidroelektrarne
višina odprtine šobe
največja višina odprtine šobe
koeficient izgub
brezdimenzijski pretočni koeficient šobe
Peltonove turbine število vrtljajev turbine moč
tlak na ravni (g - g) tlak na ravni (d - d) manometrični tlak pretok pretok šobe gib igle šobe relativni gib igle največji gib šobe specifična energija specifična energija vodnega toka na gladini
vode zgornje akumulacije specifična energija vodnega toka na gladini
vode spodnje akumulacije bruto specifična energija hidroelektrarne kota vstopnega prereza turbine kota točke, kjer os šobe dotika osnovni krog
turbinskega kolesa kot igle šobe
koeficient hitrosti iztekanja gostota vode izstopni kot šobe izkoristek izkoristek šobe hidravlične izgube v dovodnem sistemu
a
Am c
cg
cd
D1
Di
di
do
dm
H
H
br
h h
imax
k kq
n
P
pg
pd
pm
Q
Qm s s’ s
max
Y Yg
Yd Y
br
z1 z2
a
j
r
g
h
hm
DH1
distance between the elevation of the centre of gravity of the inlet cross section and the elevation of the pressure gauge fastening
surface of outlet flow cross section
flow velocity
average velocity in cross section (g – g)
average velocity in cross section (d – d)
basic diameters of runner
diameters of housing on “i - i”
diameter of needle in cross section (i – i )
diameter of water jet
diameter of nozzle outlet opening
net fall
gross fall of HEPP
height of nozzle opening
maximum height of nozzle opening
loss coefficient
non–dimensional flow coefficient of Pelton turbine nozzle
number of turbine revolutions
power
pressure at level ( g – g )
pressure at level (d – d )
gauge pressure
flow
nozzle flow
nozzle needle movement
relative needle movement
maximum nozzle movement
specific energy
specific energy of water flow on water surface of upstream reservoir
specific energy of water flow on water surface of downstream reservoir
gross specific energy of HEPP
elevation of turbine inlet cross section
elevation of point where the nozzle are s touches the basic circle of the turbine wheel
nozzle needle angle
coefficient of discharge velocity
water density
nozzle outlet angle
efficiency
nozzle efficiency
hydraulic losses in supplying system
7 LITERATURA 7 REFERENCE
[1] Ispitivanje energetskih karakteristika i prelaznih pojava na agregatima HE “Peručica” - Institut “Jaroslav Černi” (Beograd 1984, 1987, 1998).
gfin^OtJJIMISCSD
02-9
stran 499         |^BSSITIMIGC
Mrki} M. - Culafi} Z.: Nekateri vidiki terenskih preskusov - Some Aspects of Research
Naslov avtorjev:
prof.dr. Milo Mrkič prof.dr. Zoran Culafič Univerzitet Crne Gore Mašinski fakultet Podgorica Cetinjski put bb 81000 Podgorica, ZRJ milom@cg.ac.yu
Authors’ Address:    Prof. Dr. Milo Mrkič ProfDr. Zoran Culafič University of Montenegro Faculty of Mech. Eng. Podgorica Cetinjski put bb 81000 Podgorica, ZRJ milom@cg.ac.yu
Prejeto: Received:
21.2.2001
Sprejeto: Accepted:
22.11.2002
VH^tTPsDDIK
stran   500